Electrical Supply Upgrade

Basher85 wrote: »

Hey guys, I've been asked to carry out a supply upgrade for a premises, from 15kva to 20kva I am increasing the tails from 16s to 35s and the earth from 10s to 16s.

I am assuming that this is a single phase supply (as you say existing board is a standard domestic board), please correct me if I am wrong...

At 230VAC 20kVA is around 87 amps. A 35 sq. mm cable would be more than capable of carrying this current. I am sure you have considered volt drop, earth fault loop impedance etc.

However, the existing board is a standard domestic board, would I have to upgrade the board to a 100 amp rated board

The main considerations should be:
1) What rating is the main fuse?
2) Are the busbars rated for more than this rating? Is the panel flex?
3) Can you terminate 35 mm sq. cables into the main fuse and main neutral bar?
4) Have you enough space for bending radii of cables etc.? This can take up a lot of space.

Personally I would start again with a new board. Within the panel 16 mm sq. panel flex with ferrules should be fine. Ensure everything is really tight. Oversize the enclosure, it won't cost much extra and it will speed you up considerably, remember time is money too! Also you will inevitably fill the space at some stage. I would also go with RCBO's for almost every circuit. That way you can use double pole busbar for everything and the neutral bar will only have a few connections going to it. Everything becomes, neat, simple, quick and fault finding is very easy. Go for a large earth bar in the panel too, sometimes I even link two earth bars just to give me extra.

I am about to replace a distribution board myself, this is the approach I am taking.

Edit: To meet new requirements of the new rules IS10101 (that are not in force yet) consider installing a metal enclosure.